The activities of this project comprise 3 main functions: 1) the systematic study of certain groups of parasitic arthropods. The scanning electron microscope has greatly aided in elucidating taxonomic concepts in acarines actually or potentially involved in transmission of disease agents of interest to this laboratory. 2) attempted experimental arthropod transmission of such agents not under special study in other projects. 3) the colonization of potential vectors. The groups of parasitic arthropods chiefly studied are ticks and mites. Colonies of 31 species of ticks, 3 of mites, and 1 of mosquitoes are available for various investigations. Field studies augment transmission tests in the laboratory when indicated. A collaborative study with NAMRU-3 in Cairo, A.R.E., augments systematic information on ticks in various parts of the world.